120 PKOCEEDIXGS OF THE ACADEMY OF [Jan., 



evolution toward an ancestral lerauroid tritubercular dentition. It 

 appears to me that this observation of Cope's does not stand alone, 

 and my })resent purpose is to indicate certain homologies which 

 appear to fall into line with it. 



In estimating the degree of relationship between men and apes, 

 on the one hand, and eatarrhine monkeys on the other, and that 

 borne by each series to their ancestral group, two sets of homolo- 

 gies are of especial value — those which the anthropomorpha share 

 with gome, at least, among lemurs (in which eatarrhine monkeys 

 have no part), and those connecting catarrhines with lemurs, which 

 are, conversely, absent from anthropomorpha. 



Some correspondences of much weight are disclosed by the teeth 

 and the vertebral column; these will be briefly recapitulated with- 

 out extended description of details, which have already been given 

 in each case by recognized authorities, although it does not appear 

 that due weight has been given to their bearing upon the present 

 question. It may be added that almost all have been verified by 

 my own observations. 



In anthropomorpha there is an oblique ridge crossing the crowns 

 of the upper molars from jt»rofocone io meiacone.* Tliis is present 

 with great uniformity in the first and second human molars, as 

 well as in the third when it presents the quad I'i tubercular form, 

 and in examination of a considerable number of skulls belonging 

 to all four genera of anthropoids, I have found it in every case 

 where the crowns were sufficiently unworn to permit its disclosure. 

 Topinard lays much stress upon this crest and expresses the opinion 

 that it represents the posterior border of the primitive three-cusped 

 tooth," from which the four-cusped has been evolved by addition of 

 a postero-internal cusp (hypocone). He states, further,* that the 

 crest is never absent in platyrrhiue monkeys — an assertion which 

 appears to me too sweeping, but traces of it are certainly found in 

 Ateles and Alouatta, and perhaps irregularly in other genera. It 

 is not found in any eatarrhine monkey, but reappears in the 

 quadritubercular lemurs of the family Nydicchidce,'^ comprising 



*Owen, Odordografliy, PI. 116, fig. 6, and Comp. Anat., Ill, p. 320 ; 

 Huxley, Anat. Vert., pp. 390, 396, 412 (direction of ridge reversed), and 

 Proc. Zool. Soc. of London, 1864, p. 314 et scq.; Mivart, P. Z. S., 1864, 

 p. 611 et seq.; Topinard, L'Anthrojiologie, 1892, p. 641 et seq. 



* ?. c, p. 650. 



^l.c, p. 683. 



'Huxley, I. c, pp. 322-324; ]\Iivart, I. c, p. 631 ; Topiuard, I. c, p. 691. 



